Y=sinxcosx+cos2x
=1/2sin2x+cos2x
=√（1^2+1/2^2)sin(2x+α),tanα=2
=√5/2*sin(2x+α)
因为
Y=Asin(wx+β)
的最小正周期为2π/|w|
故,所求为
T=2π、2=π